DRAINAGE DIVERSION WORKS FOR THE COMPREHENSIVE RESIDENTIAL DEVELOPMENT AT VARIOUS LOTS IN DD 227 & DD 229, TAI PO TSAI, SAI KUNG - PROJECT PROFILE (Issue No.: 1)
(September 2004)
Allied Environmental Consultants Ltd.
DRAINAGE DIVERSION WORKS FOR COMPREHENSIVE RESIDENTIAL DEVELOPMENT AT VARIOUS LOTS IN DD 227 & DD 229, TAI PO TSAI, SAI KUNG - PROJECT PROFILE i
TABLE OF CONTENTS
1. BASIC INFORMATION ...... 1 1.1 Project title...... 1 1.2 Purpose and nature of project ...... 1 1.3 Name of project proponent ...... 1 1.4 Location and scale of project (include plans) and history of site ...... 1 1.5 Evaluation of Drainage Diversion Design Options ...... 2 1.6 Number and types of designated projects to be covered by the project profile...... 3 1.7 Name and telephone number of contact person(s): ...... 3 2. OUTLINE OF PLANNING AND IMPLEMENTATION PROGRAMME ...... 3
3. MAJOR ELEMENTS OF THE SURROUNDING ENVIRONMENT...... 4
4. POSSIBLE IMPACT ON THE ENVIRONMENT...... 5 4.1 Introduction...... 5 4.2 Air Quality...... 7 4.3 Noise...... 10 4.4 Ecology...... 12 4.5 Waste ...... 16 4.6 Water...... 18 5. ENVIRONMENTAL PROTECTION MEASURES TO BE INCORPORATED IN THE DESIGN AND ANY FURTHER ENVIRONMENTAL IMPLICATIONS...... 18 5.1 Air Quality...... 18 5.2 Noise...... 20 5.3 Ecology...... 22 5.4 Waste ...... 23 5.5 Water...... 25 6. ENVIRONMENTAL MONITORING AND AUDIT ...... 26 6.1 Air...... 26 6.2 Noise...... 26 6.3 Ecology...... 27 6.4 Waste ...... 27 6.5 Water...... 27 7. USE OF PREVIOUS APPROVED EIA REPORTS...... 28
8. CONCLUSIONS ...... 28
AEC DRAINAGE DIVERSION WORKS FOR COMPREHENSIVE RESIDENTIAL DEVELOPMENT AT VARIOUS LOTS IN DD 227 & DD 229, TAI PO TSAI, SAI KUNG - PROJECT PROFILE ii
LIST OF TABLES
Table 2.1 Construction Sequence and Duration Table 4.1 Potential Environmental Impacts during Construction Phase of the Proposed Drainage Diversion Works Table 4.2 Potential Environmental Impacts during Operational Phase of the Proposed Drainage Diversion Works Table 4.3 Representative Air Sensitive Receivers Table 4.4 Dust Emission Rates for Various Construction Activities – Without Mitigation Table 4.5 Maximum Predicted TSP and RSP Concentrations – Without Mitigation Table 4.6 Representative Noise Sensitive Receiver Table 4.7 Assumed Plant Inventory Table 4.8 Maximum Predicted Unmitigated Construction Noise Levels Table 4.9 Ecological Evaluation of Stream and Riparian Habitats Table 5.1 Emission Factors for Various Construction Activities – With Mitigation Table 5.2 Maximum Predicted TSP and RSP Concentrations – With Mitigation Table 5.3 Sound Power Levels of Quiet PME Table 5.4 Maximum Predicted Mitigated Construction Noise Levels Table 5.5 Recommended Plant Species to be Planted For Landscaping Purpose
LIST OF FIGURES
Figure 1.1 Site Location Plan Figure 1.2 Master Layout Plan Figure 1.3 Existing Stream Course System Figure 1.4 Layout of Existing Stream Course and Proposed Drainage Diversion Figure 1.5a-b Schematic Section of Proposed Drainage Diversion Works Figure 4.1 Location of Representative Air Sensitive Receivers Figure 4.2 Location of Representative Noise Sensitive Receivers Figure 4.3 Isopleths of Maximum hourly TSP concentration at ground floor after mitigation Figure 4.4 Isopleths of Maximum daily RSP concentration at ground floor after mitigation
LIST OF APPENDICES
Appendix A Tentative Development Programme for the Entire Residential Construction Development Appendix B Works Area Plan & Proposed Sequence for Drainage Diversion Works Appendix C Preliminary Ecological Review Report Appendix D Freshwater Fish Investigation Survey Report Appendix E Calculation Sheet of Emission Factors for Construction Dust Emission Appendix F Sample Output Files of ISCST3 Model for Construction Dust Emission Appendix G Worksheet of Construction Noise Prediction Appendix H Proposed Purpose-built Noise Barrier with the Application of Quiet PME Appendix I Landscape Master Plan and Conceptual Design of Dragonfly Pond
AEC DRAINAGE DIVERSION WORKS FOR COMPREHENSIVE RESIDENTIAL DEVELOPMENT AT VARIOUS LOTS IN DD 227 & DD 229, TAI PO TSAI, SAI KUNG - PROJECT PROFILE 1
1. BASIC INFORMATION
1.1 Project title
Drainage diversion works for the comprehensive residential development at various Lots in DD227 & DD229, Tai Po Tsai, Sai Kung.
1.2 Purpose and nature of project
This project involves diversion works of existing stream courses within the subject site into an underground channel, which will receive runoff from the surrounding sub-catchments and effluent from sewage treatment plant at the future development, and discharge to Pak Shui Wun.
1.3 Name of project proponent
Addlight Investments Limited
1.4 Location and scale of project (include plans) and history of site
• The subject site is located at the southern side of University Road and is adjoining with the Tai Po Tsai Village and Clear Water Bay Road along its western boundary. This subject site is zoned as “Comprehensive Development Area” in the Outline Zoning Plan. A large part of the application site was previously used as golf driving range which was vacated a few years ago. Majority of the area is grossly vegetated, mixed with overgrown and climbers. Figure 1.1 shows the location of the subject site and its surrounding environment.
• A few stream courses flow through the site originating on the south-east slopes of Razor Hill and the promontory occupied by TV City in the south. North of the Site the main stream course joins others flowing east and north to Port Shelter in a steep ravine above Pak Shui Wan beach.
• The subject site covers an area of 6.68 ha. A total of 939 residential units will be provided. Since an existing stream is running across a substantial part of the site, it is proposed that the section of stream within the subject site will be diverted into an underground channel to receive runoff from the surrounding sub-catchments. This work involves the diversion of approximately 600m of the existing stream channel. Figure 1.2 shows the master layout plan of the proposed residential development in relation to the existing stream and the proposed box culvert. Figure 1.3 shows the existing stream course system and Figure 1.4 shows the location of the existing stream course and the proposed drainage diversion.
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1.5 Evaluation of Drainage Diversion Design Options
For the proposed drainage diversion works, two selected design options are considered in details and a brief evaluation of these options is given below.
Option 1 – Open Channel
• By adopting an open channel with natural bottom design, the potential ecological impact associated with the drainage works is reduced. The natural bottom channel would provide habitat for native species if properly set up and maintained.
• However, the existing stream collects sewage discharge from Tai Po Tsai Village as well as contaminated surface run off. An open channel poses potential hygienic and environmental problems. It also may cause unpleasant odour and visual impact on the neighbourhood as well as the proposed development.
• In view of the linear shape of the subject site, there is insufficient space to accommodate an open channel design with provision of an 8.5m utility and drainage reserve, a reserve for utility and an access road, which allows for easier maintenance by DSD as well as Utility undertakers.
• The open channel scheme would also inevitably pose an unjustifiable risk to fall at height, with consideration to the level difference of the formed ground and channel invert. Therefore, after accommodating an open channel at the subject site, there would be insufficient space to locate the access road and utility reserve required for the operation of the development. The entire 8.5m wide utility and drainage reserve will have to be fenced off for safety reasons.
• In response to Planning Department’s comment to encourage more area should be used for landscaping, a substantial landscape master plan has been proposed for the subject site. After accommodating an open channel, the area available for landscaping is significantly reduced. This would jeopardize the provision of compensationary planting proposal (with 1229 trees need to be planted within the site in the approved Landscape Master Plan).
Option 2 – Underground Box Culvert
• For effective gravity flow, the alignment of the proposed drainage diversion should follow the lower topography of the site in lieu of climbing uphill along the eastern boundary of the site. A route along the eastern boundary of the site would require a deep drainage channel of approximately 9m depths, which is not acceptable from maintenance point of view. This drainage channel will also need to intercept flows originated from Razor Hill to the west of the site, therefore, having drainage route locating on a high terrain causes difficulty for connections and possibility of backflow. The underground box culvert design, which is not constrained by topography, can provide a comprehensive solution to address these issues.
• By adopting the underground box culvert design, the potential environmental nuisance associated with open channel flow that may be caused to the neighborhood and the proposed development is alleviated.
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• The underground box culvert design also can prevent direct contamination of the stream course, including the downstream Conservation Area and Coastal Protection Area, from unexpected human activities and surface run-off from the subject development.
• The underground box culvert scheme has the benefit of incorporating the required utility and drainage reserve and complies with the Utility Undertakers statutory requirements.
• By adopting the underground box culvert design, there would be minimal impact on the implementation of landscape master plan.
In view of the above, the underground box culvert option is considered more suitable for the subject site from both engineering and environmental point of view. Figure 1.5a and 1.5b illustrate schematic sections of the proposed drainage diversion works. The works area plan and proposed sequence of drainage diversion works are given in Appendix B.
1.6 Number and types of designated projects to be covered by the project profile
The diverted stream will discharge into an area that is less than 300m from the nearest boundary of an existing Conservation Area and Coastal Protection Area. The proposed diversion works constitutes a Designated Project of type I.1(b) in Schedule 2 of the EIAO.
1.7 Name and telephone number of contact person(s): • Project Proponent: Addlight Investments Limited, Ms. Viola Cheng (Tel. No.:2844 3291) • Environmental Consultant: Allied Environmental Consultants Limited, Ms. Grace Kwok (Tel. No.: 2815 7028)
2. OUTLINE OF PLANNING AND IMPLEMENTATION PROGRAMME
The drainage diversion is being planned and designed by Addlight Investments Limited and their appointed Consultants. It is proposed that the works will commence in mid late of 2005 for approximately 18 months. Tentative development programme of the entire residential projects is presented in Appendix A, while a detailed breakdown of the 18-month duration of the proposed drainage diversion work is shown in Table 2.1 below:
Table 2.1 Construction Sequence and Duration Major construction activities Duration (months) Mobilization and sheet piling installation 2.5 Grout curtain and pumping test 2 Test report and consent application 1.5 Excavation and construction of box culvert 9 Connection works and diversion 1.5 Backfilling and compaction 1.5 Total 18
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The following is a brief description of the construction sequence for the drainage diversion works at the conceptual design stage. Appendix B illustrates sequence of the drainage diversion works. A detailed sequence of works shall be proposed by the Main Contractor prior to the actual commencement of works.
Stage 1
1. Mobilization of plants for the drainage diversion works.
2. Install sheet piles to the required depths.
Stage 2
3. Excavate to the proposed final excavation level for box culvert and pipe laying works. Suitable excavated soils should be stored temporarily at the designated areas on site with protective measures for future backfilling works.
4. Temporarily divert the portion of the existing stream, which overlaps with the proposed box culvert and pipe drainage line, within the proposed works area.
5. Deliver precast concrete box culvert and pipe sections to site.
6. Place and connect box culvert and pipe sections along the proposed drainage line.
Stage 3
7. Construct drainage facilities such as sand traps and catch pits at intersections between the proposed drainage line and existing sideline streams.
8. Divert water from existing streams to the proposed drainage line.
Stage 4
9. Backfill the cut slopes around the proposed drainage line to the required level for protection of the completed drainage system and safety reasons.
3. MAJOR ELEMENTS OF THE SURROUNDING ENVIRONMENT
• The subject site is surrounded by village houses and University staff housing. HKUST and TV city are situated to the east and to the south of the subject site respectively.
• Sensitive receivers which are located within 500m of the site includes: ¾ Coastal protection area in Pak Shui Wan; ¾ Conservation area located at the north of the subject site; ¾ Residential buildings: Pik Shui Sun Tsuen and university staff housing to the north of the site, Tai Po Tsai Tsuen to the west of the site, and TVB staff hostel to the south of the site. ¾ Educational Institutions: Clearwater Bay School and HKUST to the south and to the east of the subject site.
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• The local traffic network such as the Clear Water Bay Road and University Road are considered to be the dominant air pollution and noise pollution sources in the study area. No industrial uses are located within the area.
• According to the Clear Water Bay Peninsula North Development Permission Area Plan No. DPA/SK-CWBN/2, the subject site is known as CDA(1). Another CDA located south of the subject site which is intended for the redevelopment of the Shaw Brothers’ Studio is known as CDA(2). Pursuant to the Town Planning Ordinance, development/redevelopment within the CDA zone is subject to the approval of the Town Planning Board (TPB). Planning approval to the residential development on the subject development site (CDA(1)) has been obtained from the TPB on 28.6.2002. The concerned developer of the CDA(2) site has yet to obtain any planning approval from the TPB. Even when planning approval is obtained, it would usually require one to two years to fulfill a list of approval conditions and deposit the Master Layout Plan in the Land Registry before the construction works could be commenced. Since the subject site (CDA(1)) and the nearby CDA(2) site are at different development stages, it is anticipated that there shall be no concurrent construction works at the two. Besides, the CDA(1) construction works will not overlap with the proposed drainage diversion works in this study.
• A Preliminary Ecological Review Report has been conducted by China-Hong Kong Ecology Consultants Company. The report concluded that the existing habitat quality of the stream and riparian habitats within the project site is considered low as a result of poor aquatic fauna and human disturbance. A Preliminary Ecological Review Report detailing the findings of the study is attached in Appendix C.
• A freshwater fish investigation has been conducted by Ichthyology. The survey results indicated that the water quality of the existing stream is stressed through the effect of pollution from various human activities in the past such as farming and construction works. Existing water pollution sources generally related to the domestic effluents generated in the surrounding area. There was no native fish individuals found in the entire target stream course except for a few introduced fish species. A Freshwater Fish Investigation Survey Report is attached in Appendix D.
4. POSSIBLE IMPACT ON THE ENVIRONMENT
4.1 Introduction
The potential environmental impacts associated with the proposed drainage diversion works are assessed according to the criteria given in the Technical Memorandum on Environmental Impact Assessment Process (TMEIA). The potential impacts during the construction and operation phases of the drainage diversion works are shown in Table 4.1 and Table 4.2 respectively.
Table 4.1 Potential Environmental Impacts during Construction Phase of the Proposed Drainage Diversion Works Environmental Issues Construction Phase Possible Impact Gaseous emissions Unlikely to cause impact
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Environmental Issues Construction Phase Possible Impact Dust Fugitive dust emissions from site clearance, rock-breaking, excavation and vehicle movement on unpaved road Odour Unlikely to generate odour Noisy operations Noise from operation of PME and prescribed construction works such as handling of steel bars, hammering and formworks Night-time operation No construction activities will be carried out during night-time Traffic generation Heavy vehicles for transportation of construction material may slightly increase the traffic flow in the vicinity Liquid effluents, Surface runoff and wastewater generation discharges, or from construction activities. contaminated runoff Generation of waste or by- Construction waste, such as wood boards products and excavated soil
Dangerous goods, Unlikely to store dangerous goods, or hazardous material or generate hazardous materials or wastes wastes Risk of accidents Unlikely to cause risk of accidents which would result in pollution or hazard Disposal of spoil material Unlikely to cause impact
Disruption of water Unlikely to cause disruption of water movement or bottom movement or bottom sediment sediment Dredging of stream Unlikely to cause impact sediment Unsightly visual Unlikely to cause long term impact as the appearance construction works only last for about 18 months Ecological impacts Impacts on fauna and flora
Table 4.2 Potential Environmental Impacts during Operational Phase of the Proposed Drainage Diversion Works Environmental Issues Operational Phase Potential Impacts Gaseous emissions No chimney or gaseous emissions installation Dust Unlikely to cause impact Odour Unlikely to cause impact Noisy operations Unlikely to cause impact Night-time operation Unlikely to occur
Traffic generation Unlikely to occur
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Environmental Issues Operational Phase Potential Impacts Liquid effluents, Unlikely to cause impact discharges, or contaminated runoff Generation of waste or by- Unlikely to cause impact products Dangerous goods, Unlikely to store dangerous goods, hazardous material or generate hazardous materials or wastes wastes Risk of accidents Unlikely to cause risk of accidents which would result in pollution or hazard Disposal of spoil material Unlikely to occur
Disruption of water Unlikely to occur movement or bottom sediment Dredging of stream Unlikely to occur sediment Unsightly visual Unlikely to occur as the diverted channel appearance is located at underground level Ecological impacts Impacts on fauna
In summary, the potential impacts associated with the proposed drainage diversion works include dust emission, noise impact, wastewater generation, waste generation and ecological impact during construction phase as well as ecological impact during operational phase. These potential impacts have been assessed and the findings are detailed in the following sections.
4.2 Air Quality
The construction activities that have the potential to generate dust include material handling, rock breaking, excavation, wind erosion and truck haulage on unpaved roads. Exhaust emissions of SO2 and NO2 from diesel-powered mechanical equipment will also be generated. The extent of impacts depend on the distances between the work sites and the identified Air Sensitive Receivers (ASRs), the construction methods employed, the number of plants used and frequency of vehicle movements.
Information on the representative ASRs identified in the vicinity of the subject site is presented in Table 4.3. Location of the representative ASRs is illustrated in Figure 4.1. The worst-case concentrations of dust emission from the construction works are predicted at elevations of 1.5m above the ground floor and 2nd floor level of the representative ASRs identified.
Table 4.3 Representative Air Sensitive Receivers ASR ID Description Sensitive Uses Distance from Work Site Boundary (m) A1 Tai Po Tsai Tsuen Domestic Premises 170 A2 Staff Housing Hostel 231 AEC
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ASR ID Description Sensitive Uses Distance from Work Site Boundary (m) (Block A) A3 Staff Housing Hostel 158 (Apartment 1-12) A4 Principal Housing Hostel 210 A5 HKUST Educational Institution 194 A6 TVB Staff Quarter Hostel 320 A7 Clearwater Bay School Educational Institution 199 A8 Tai Po Tsai Tsuen Domestic Premises 12 A9 Tai Po Tsai Tsuen Domestic Premises 13 A10 Tai Po Tsai Tsuen Domestic Premises 64
Air Quality Objectives (AQO) have been set by the Hong Kong Environmental Protection Department (EPD) for seven main urban air pollutants including the pollutant of concern in this project, Total Suspended Particulates (TSP) and Respirable Suspended Particulates (RSP). The 24-hour AQO for TSP and RSP are 260µg/m3 and 180µg/m3 respectively, which should not be exceeded more than once per year. The 1-hour TSP criteria for construction dust as specified in the Technical Memorandum on Environmental Impact Assessment Process (TMEIA) is 500µg/m3.
In order to evaluate the potential air quality impacts on the neighbouring ASRs during the construction phase of the drainage diversion works, the dust emissions, measurable as Total Suspended Particulates (TSP) and Respirable Suspended Particulates (RSP), from various on-site construction activities are assessed under the worst-case scenario. The dust emission rates are estimated based on the emission factors compiled in the AP-421 and other available data. Detailed calculation of the emission factors adopted in the dust modelling is presented in Appendix E. Table 4.4 gives the dust emission rates adopted in the modelling.
Table 4.4 Dust Emission Rates for Various Construction Activities – Without Mitigation Dust Emission Rates Activities Remarks TSP RSP Based on USEPA AP-42 (1) Material 4.33 x 10-3 g s-1 2.05 x 10-3 g s-1 Vol. 1 5th Edition, Handling Section 13.2.4.3 Based on USEPA AP-42 (2) Rock 3.69 x 10-6 g s-1 1.92 x 10-6 g s-1 Vol. 1 5th Edition, Table Breaking 11.9-4, Equation (1) Based on USEPA AP-42 (3) Excavation 1.16 x 10-2 g s-1 5.47 x 10-3 g s-1 Vol. 1 5th Edition, Section 13.2.4.3 (4) Vehicle Based on USEPA AP-42 Movements on 1.15 g s-1 3.12 x 10-1 g s-1 Vol. 1 5th Edition, Unpaved Site Section 13.2.2 Roads Based on USEPA AP-42 (5) Wind Erosion 2.695 x 10-6 g s-1m-2 1.348 x 10-6 g s-1m-2 Vol. 1 5th Edition, Table
1 Compilation of Air Pollution emission Factors, AP-42, 5th Edition, United States Environmental Protection Agency, January 1995 AEC
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Dust Emission Rates Activities Remarks TSP RSP 11.9-4 = (1)+(2)+(3)+(4)+(5) Total Emission 6.12 x 10-5 g s-1m-2 1.73 x 10-5 g s-1m-2 Total site area
The assessment is carried out using the dispersion model Industrial Source Complex Short Term (ISCST3). The basis of the model is the linear, steady-state Gaussian plume equation. The 2001 meteorological data (full year), as monitored by the Hong Kong Observatory at the Sai Kung Weather Station, is used as model input parameter. The average background levels of 83.6µg/m3 for TSP and 54.4µg/m3 for RSP from Kwun Tong Air Quality Monitoring Station from Year 1997 to Year 2001 are incorporated into the modelled results.
The maximum predicted hourly and daily TSP levels, and daily RSP at 1.5m above local ground level and 2nd floor level at the identified ASRs are shown in Table 4.5 below. Sample output files of the ISCST3 model are given in Appendix F. It should be noted that these worst-case prediction results represent the highest dust concentrations predicted to occur in a year under particular weather conditions. The dust concentrations at other times could be far less than these values.
Table 4.5 Maximum Predicted TSP and RSP Concentrations – Without Mitigation ASR 1- hour Averaged TSP 24-hour Averaged TSP 24-hour Averaged RSP ID Concentration, µg/m3 Concentration, µg/m3 Concentration, µg/m3 G/F 2/F G/F 2/F G/F 2/F A1 921.80 420.17 264.21 147.13 105.45 72.36 A2 646.49 454.45 195.35 144.30 85.99 71.56 A3 1000.94 645.32 294.05 176.58 113.89 80.68 A4 672.10 372.19 246.94 173.83 100.57 79.91 A5 946.71 388.50 279.43 173.95 109.76 79.94 A6 735.56 427.83 242.70 173.42 99.37 79.79 A7 974.96 409.90 318.06 181.80 120.68 82.16 A8 2377.62 531.30 823.29 209.44 263.49 89.97 A9 2018.94 582.99 750.93 213.56 243.04 91.14 A10 1090.70 497.38 391.15 169.80 141.34 78.77 Remarks: Results include annual TSP background level of 83.6µg/m3. TSP – recommended 1-hour TSP criterion (500µg/m3) and AQO for 24-hour TSP (260µg/m3) Results include annual RSP background level of 54.4µg/m3. RSP - AQO for 24-hour RSP (180µg/m3) Bold and italic figures indicate exceedance of respective air quality criteria
The worst-case prediction results indicate that without mitigation, the hourly TSP criterion is likely to be exceeded at ground floor level of the ASRs. Whereas at the 2nd floor, exceedance of the hourly TSP criterion occurs at A3 (Staff Housing Apartment), A8 (Tai Po Tsai Tsuen) and A9 (Tai Po Tsai Tsuen). The AQO for daily TSP is likely to be exceeded at ground floor level of most of the ASRs except A2 (Staff Housing), A4 (Principal Housing) and A6 (TVB Staff Quarter), whereas no exceedance of the AQO for daily TSP is predicted at the 2nd floor of all ASRs. The AQO for daily RSP is likely to be exceeded at the ground floor of A8 (Tai Po Tsai Tsuen) and A9 (Tai Po Tsai Tsuen), whereas no exceedance is predicted at the 2nd floor of the ASRs. Therefore, the assessment
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results show that dust control measures will be required to ensure compliance with the hourly TSP criterion and the AQOs for TSP and RSP.
Since only limited number of construction equipment will be used on-site during the construction of the drainage diversion, the overall exhaust emission from diesel-powered mechanical equipment of these plants is expected to be insignificant and unlikely to cause adverse air quality impact. No operational phase air quality impact as a result of the proposed drainage diversion is anticipated.
4.3 Noise
Noise impacts arising from construction of the proposed drainage diversion are mainly due to the use of powered mechanical equipment (PME) for various construction activities, including site clearance, sheet piling, excavation, connection works and backfilling. The construction period is estimated to last for about 18 months. It is anticipated that construction work shall only be carried out during daytime. The potential noise impact during the construction phase of the proposed drainage diversion is assessed quantitatively.
Information on the representative Noise Sensitive Receivers (NSRs) identified within 300m radius of the subject site is presented in Table 4.6. Location of the representative NSRs is illustrated in Figure 4.2. The worst-case construction noise levels during different work stages are predicted at the representative NSRs identified.
Table 4.6 Representative Noise Sensitive Receiver Slant Distance Between Centre of NSR ID Description Sensitive Uses Site Section and NSR (m) N1 HKUST Staff Quarter Hostel 222 N2 HKUST Staff Hostel 162 Residence (Apartment 1-12) N3 Tai Po Tsai Village Domestic Premises 75 N4 Tai Po Tsai Village Domestic Premises 48 N5 Tai Po Tsai Village Domestic Premises 21 N6 Tai Po Tsai Village Domestic Premises 46 N7 HKUST Educational Institution206 N8 Tai Po Tsai Village Domestic Premises 84 N9 Tai Po Tsai Village Domestic Premises 101 N10 Clearwater Bay School Educational Institution 250
There is no statutory control on construction activities during non-restricted hours in daytime. However, construction noise criteria of LAeq(30min) 75dB(A) and 70dB(A), respectively for dwellings and schools are recommended in ProPECC PN2/93 and commonly used as noise assessment criteria for daytime construction works.
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In order to evaluate the potential noise impacts associated with the construction of the drainage diversion works during different work stages, the construction noise levels are predicted at the neighbouring NSRs under the worst-case scenario of assuming all construction plants in full operation. The construction noise assessment is conducted in accordance with the method prescribed in the “Technical Memorandum on Noise from Construction Work other than Percussive Piling”. Derived from a preliminary construction work schedule, an assumed plant inventory as shown in Table 4.7 has been adopted as the basis of the noise assessment. Table 4.7 Assumed Plant Inventory Work Stage Reference PME No. of SWL, code in items dB(A) per TM item 1. Mobilization and sheet 102 Generator, silenced 2 100 piling installation # 081 Excavator 2 112 2. Excavation construction of 001 Air compressor 1 100 box culvert 102 Generator, silenced 2 100 081 Excavator 3 112 141 Lorry 3 112 Poker, vibratory, 170 2 113 hand-held 186 Roller, vibratory 2 108 Mobile crane 048 2 112 (diesel) 3. Connection works & 001 Air compressor 1 100 diversion 102 Generator, silenced 1 100 Mobile crane 048 1 112 (diesel) 081 Excavator 1 112 141 Lorry 1 112 Concrete lorry 044 1 109 mixer 047 Concrete pump 1 109 Compactor, 050 2 105 vibratory 4. Backfilling & compaction 001 Air compressor 1 100 102 Generator, silenced 1 100 081 Excavator 3 112 141 Lorry 3 112 186 Roller, vibratory 2 108 #Remark: Sheet piling installation shall be carried out using hydraulic type percussive piling method. Since noise generated through percussive piling is controlled under the Noise Control Ordinance, construction noise permit shall be applied by the Contractor before commencement of piling work.
The maximum predicted unmitigated construction noise levels at the representative NSRs are summarized in Table 4.8 below.
Table 4.8 Maximum Predicted Unmitigated Construction Noise Levels
Receiver ID Noise criteria Predicted Noise level, Leq (30min) , dB(A) AEC
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Stage 1 Stage 2 Stage 3 Stage 4 N1 75 63 71 67 68 N2 75 66 74 70 71 N3 75 72 80 76 77 N4 75 76 84 80 81 N5 75 84 92 88 89 N6 75 77 85 81 82 N7 70 64 72 68 69 N8 75 71 79 75 76 N9 75 70 78 74 75 N10 70 62 70 66 67 Remarks: Construction noise criteria for dwellings and schools are LAeq(30min) 75dB(A) and 70dB(A) respectively. Bold and italic figures indicate exceedance of noise criteria.
The prediction results indicate that without mitigation, the construction activities associated with the proposed drainage diversion works are likely to give rise to noise levels that exceed the recommended noise criteria at most of the nearby NSRs. The maximum construction noise level of 92dB(A) is predicted during the stage of excavation and construction of box culvert at N5, which is potentially the worst-affected location due to its close proximity to the work site. Detailed worksheet of construction noise calculation is given in Appendix G. Noise mitigation measures are therefore required to reduce the potential noise impacts to acceptable levels during the construction of the drainage diversion works.
No operational phase noise impact as a result of the proposed drainage diversion is anticipated.
4.4 Ecology
4.4.1 Terrestrial Ecological Impacts
The potential terrestrial ecological impacts arising from the construction activities generally include direct impacts due to habitat loss and indirect impacts due to construction activities such as increased human activities or disturbance.
A Preliminary field surveys on riparian vegetation, mammals, birds, reptiles, amphibians, dragonflies and butterflies were undertaken in August and September 2003 to study the potential impact of the proposed project on other fauna groups (e.g. birds and dragonfly) and the riparian vegetation along the stream course. A Preliminary Ecological Review Report detailing the findings of the study is attached in Appendix C.
The findings of the field surveys are summarized as follows:
z There was no rare or protected plant within the subject site. Most common riparian and plants at the surveyed area were mixture of native and exotic or introduced species. In addition, no rare or protected plants were recorded from the stream bed. Common species of birds, amphibians and reptiles which are widely distributed in similar habitats in the New Territories were recorded.
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z Dragonflies were found common at the site as the stream and riparian habitats provided feeding and foraging ground for the animals. All those recorded species were either common or very common species in Hong Kong.
z Butterflies species recorded at the site are also widely distributed and commonly found in Hong Kong.
z As the site is human disturbed, mammals was scarce, with only feral dogs, cats and common bat encountered at the site.
Ecological evaluation of stream and riparian habitats are summarized in Table 4.9
Table 4.9 Ecological evaluation of stream and riparian habitats Criteria Evaluation Naturalness • Most of stream and its riparian habitats were human disturbed due to past and existing land uses including residents, plant nursery, car park and other commercial and infrastructure facilities in the vicinity. The stream received domestic discharge from nearby developments and steam water was apparently polluted. Size • Low to Medium (~600m in length) comparing to approximately 2.5km total length of the stream. Diversity • Diversity of aquatic life (fish and invertebrate) is low. Plant diversity is also low and no rare or protected plants were recorded within the site. The site was heavily vegetated by exotic plants such as Mikania micrantha. About 10 species of Odonata species were recorded from the site, within indicated that the habitat support medium diversity of the aquatic fauna (though some species may come from outside habitats). Rarity • Species of fauna and flora recorded were common species. The habitat was common. Re-creatability • Constrained by land availability Fragmentation • Fragmented as a result of stream side development in the past Ecological Linkage • Linked with down and upper stream riparian habitats Potential Value • Potential habitat for a small number of freshwater fish, amphibians, dragonflies and other fauna • Feeding ground for some common birds Nursery/breeding • Potentially for some common fauna ground Age • Not determined Abundance/richness • Low wildlife
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Criteria Evaluation Ecological value of • Existing ecological value was considered low. the habitat While aquatic fauna could be colonized at the habitat if the discharge of domestic sewage and other non-point source water pollutant into the stream could be eliminated.
Construction Phase Impacts
The proposed drainage diversion would involve diverting the section of stream within the subject site into an underground channel, resulting in the loss of some 600 meters of open stream channel habitat. The whole stream was estimated to be approximately 2.5 km in length. About one quarter of the stream course was potentially affected by the proposed drainage diversion. The severity of the potential impact associated with direct loss of open stream habitat is somewhat lessened by the fact that the stream and riparian habitats do not support protected flora and fauna and its small scale.
Given the surrounding land uses, commercial facilities and village house development in the catchment, the proposed site is largely with low ecological value. Loss of the open feature of the affected stream section would only affect some exotic fish species and other common fauna in localized area. As the affected stream section is human disturbed and receives sewage discharge from nearby developments, there is little potential for recolonization and rehabitation of the polluted stream section given the current development conditions in the vicinity. The impacts associated with the loss of this section of the stream was considered limited.
Impacts on stream fauna may arise from any of the following sources: Sedimentation of streams by construction activities and runoff or dust; pollution of streams by spilled construction materials; culverting of streams and filing of stream meander. Sedimentation of streams by runoff from construction sites would occur if not controlled. Heavy sedimentation may cause temporal de-fauna of the stream and may affect feeding and breeding habitats for aquatic insects, crustaceans, fishes and frogs. If the conditions were severe, the lower stream course, which flows through the Conservation Area and discharges to the Coastal Protection Area at Pak Shui Wan, outside the subject site, may also be affected by sedimentation of uncontrolled discharge or run-off from the construction site.
During the proposed drainage diversion works, the water flow at the existing stream section within the subject site shall be maintained until the construction of the new drainage channel is completed and ready for diversion. Therefore, the proposed drainage diversion would not introduce significant changes in hydrological characteristic in upper and lower stream course during both construction and operational phases. The potential sedimentation impact during the construction phase would be temporal and could be minimised when appropriate measures are adopted at the construction site. The likely affected habitat would be re-colonised by aquatic organisms during post project period.
The proposed drainage diversion would modify open stream course within the subject site to covered channel, which would affect animals using the riparian vegetation, open stream course, and those feeding on epilithic algae on rock surface of the stream bottom. The ecological impact is considered not significant given the low ecological value of the existing fauna and flora in the affected stream section and riparian habitats. There are similar habitat features exist at some sections of the lower and upper stream course. Some
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of the affected stream fish and other fauna including bird within the application site could potentially use those habitats. When the water quality in the catchment improved, some more aquatic organisms are expected to colonise the upper and down stream.
According to the development proposal previously approved by the Planning Department, all of the approximately 83 existing trees within the development site would be retained in- situ and no additional trees would be felled as a result of the proposed residential development and the drainage diversion works.
Operational Phase Impacts
Disposal of Domestic Effluent: Discharge of untreated or partially treated effluent from the development has the potential to cause pollution and eutrophication of aquatic environment. For this reason, the domestic effluent will be collected for proper treatment and disposal in accordance with EPD’s requirements. Under the previously approved planning application, the developer has committed to provide a private sewage treatment plant within the subject site since there is no public sewerage system existing in the area for the time being. The sewage arising from the development will be treated to a standard acceptable to EPD and discharged to the proposed drainage system along the access road. With adequate treatment of domestic effluent, it should be possible to eliminate any potential pollution and eutrophication that may be caused to the lower stream course. Therefore, impacts of operation phase to stream and nearby wildlife would not be significant.
Predicted Residual Impacts
Predicted residual impacts are those impacts expected to remain after mitigation. Based on the assumption that effective and appropriate mitigation measures will be incorporated during the construction and operation of the proposed development, residual impacts for habitat loss predicted "minor". Potential construction phase impact on the lower stream course, the Conservation Area and the Coastal Protection Area at Pak Shui Wan, are temporal and could be minimized with the adoption of appropriate mitigation measures.
4.4.2 Aquatic Ecological Impacts
Fish surveys were undertaken in areas between the HKUST and Tai Po Tsai of Sai Kung during daytime and evening on 8th and 20th July 2003. Night survey was also undertaken from 6 p.m. – 2 a.m. on 11th – 12th July 2003. A Freshwater Fish Investigation Survey Report is attached in Appendix D.
A total of 83 fish individuals (including 39 captured individuals) were recorded in the upper-mid to middle course. None of the native fish individuals was seen within the survey areas (upper to middle course). All recorded individuals belong to introduced fish species. The absence of native fish individuals in the entire target stream course may be due to unsuitable condition of the habitats, including heavily modified environment and discharge of polluted water that led to intolerable worsened water quality especially in the dry season.
The water quality of the existing stream is stressed through the effect of pollution from various human activities in the past such as farming and construction works. Existing water pollution sources generally relate to the domestic effluents generated in the surrounding area.
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For the existing aquatic ecological value is low, it is anticipated that the construction work of the proposed drainage diversion will be unlikely to pose adverse impact on the stream. During operation phase, there will be a loss of habitat in the section of the stream to be diverted to underground drainage.
4.5 Waste
The types of wastes which are likely to be generated during the construction of the stream course diversion include the following: z Construction and Demolition (C&D) material z Chemical wastes z Excavated materials z Municipal wastes
The contractor undertaking the drainage diversion works shall be required to prepare a waste management plan and implement good practices to ensure proper handling and disposal of the construction waste.
4.5.1 Construction and demolition materials
The C&D materials will arise from a number of activities during site clearance, excavation and sheet piling construction and typically could be divided into two categories according to whether they are inert or non-inert. Inert material such as debris, rubble, earth and concrete shall be disposed of at public fill. The remaining C&D material contains mainly non-inert materials such as bamboo, timber, vegetation, packaging waste and other organic material shall be disposed of at designated landfill site. The anticipated C&D materials arising from this project are:
y Wood from formwork and falsework; y Scrap metals from off-cuts, re-bar, steel pipes and packaging y Plastic and paper from per-formed products and packaging. y Unstable/surplus concrete/grout; and y Damaged/contaminated construction materials.
The Construction and demolition materials arising from the construction of the drainage diversion are expected to be minimal with the adoption of good waste management practices.
4.5.2 Excavated materials
It is anticipated that approximately 36,000m3 of excavated materials will be removed for the proposed drainage diversion, of which 90% will be soil, and 10% will be rock material. It is the intention to reuse as much of the material as possible on site. About 80% (~29,000m3) of excavated material will be stockpiled for reuse at backfilling of the proposed underground drainage or the existing stream during site formation at a later stage.
The remaining unsuitable material, 20% (~7,000m3) of the excavated material, will be transported off-site to a public fill facility in Tseung Kwan O.
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4.5.3 Chemical wastes
Construction plant and vehicle servicing will likely be the primary source of chemical wastes during the construction period. The major chemical waste arising from the construction sites are likely to be oils, lubricants, and solvents. Oil waste may be in the form of raw waste, or as sundries such as spent oil filters, or materials used to absorb oil leaks. Lubricant wastes are likely to be generated from the maintenance of vehicles and mechanical equipment. The amount of chemical waste is estimated to be less than 1m3 per month.
Based on the Waste Disposal (Chemical Waste) (General) Regulation, chemical waste should be stored in a locked, fully bunded area which is impermeable to both water and the waste being stored. The waste storage area should also be covered to prevent rainfall from accumulating by volume of the chemical waste stored in that area. Appropriate spill absorption material should be stored near the storage area in order to clean up any minor spill events.
If chemical wastes are to be generated, the contractor will need to register with EPD as a chemical waste producer and observe the requirements for chemical waste storage, labelling, transportation and disposal. The contractor should follow the requirements and recommendations given in "A Guide to Chemical Waste Control Scheme: A Guide to the Registration of Chemical Waste Producers" and the "Code of Practice on the Packaging, Labelling and Storage of Chemical Wastes". All chemical wastes should be collected from site by a licensed chemical waste collector and disposed of at an appropriate disposal facility, namely the Chemical Waste Treatment Centre (CWTC) at Tsing Yi.
4.5.4 Municipal Waste
Workers will generate municipal wastes such as food wastes, packaging and wastepaper. For estimating the quantity of municipal wastes, EPD’s average value 1.07kg/employee/day has been adopted (Monitoring of Municipal Solid Waste 1996, EPD (1997) Hong Kong Government). The total volume of waste generated depends on the number of workers to be employed on site.
It is anticipated that the number of workers and site staff to be employed at peak times is less than 20. Considering 6 working days per week, the amount of municipal waste generated will be around 128.4kg/week (maximum). Disposal will be the responsibility of the Contractor who shall, in accordance with general avoidance of nuisances measures (required under the Contract), remove material at such a frequency to avoid nuisance.
The estimated sewage arising from the workforce during the construction phase is estimated to be 6.0m3/day according to the Sewerage Manual (Part 1), DSD, 1995. Facilities such as mulching or chemical toilets (disposal off-site) shall be provided especially to ensure that no sewage is discharged directly into receiving environment. With the provision of such sanitary facilities and implementation of proper management and cleaning procedure, no adverse impact is anticipated on receiving environment.
A temporary refuse collection facility should be set-up by the contractor and wastes should be stored in appropriate containers prior to collection and disposal.
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4.6 Water
Existing pollution sources within the subject site are generally related to the domestic effluents generated by Tai Po Tsai Tsuen and associated village houses. The proposed drainage diversion involves various activities which potentially affect the water quality and impact on the water sensitive receivers. These are primarily:
• the excavation works that may lead to sedimentation and reduced water quality; • the construction works which have the potential to cause spillages into the receiving waters during construction; • maintenance issues including disposal of silt from the streambed; • wash water from vehicles and equipment and dust suppression; • sewage generated due to site workers; and • run-off from site surfaces, material stock piles and drainage channels.
As toilets will be provided for workforce and pollution control measures will be in place to avoid off-site run-off, the generation of waste-water is anticipated to be minimal and controlled during construction and the impact are considered to be minor.
5. ENVIRONMENTAL PROTECTION MEASURES TO BE INCORPORATED IN THE DESIGN AND ANY FURTHER ENVIRONMENTAL IMPLICATIONS
5.1 Air Quality
In order to ensure that the potential dust emission impact during the construction phase of the proposed drainage diversion works is minimised, the following dust control measures, as stipulated in the Air Pollution Control (Construction Dust) Regulation, should be implemented during the construction of the development.
• The area in which excavation takes place should be sprayed with water immediately prior to, during and immediately after the excavation to minimise dust generation.
• Any debris from the construction should be covered entirely by impervious sheeting or stored in a sheltered debris collection area.
• Any dusty material remaining after a stockpile of cement or other materials is removed should be wetted and removed from the surface of roads.
• Every stock of more than 20 bags of cement should be covered entirely by impervious sheeting or placed in a sheltered area.
• Cement bags or any other dusty materials collected during the work should be disposed of in totally enclosed containers.
• All dusty materials should be sprayed with water immediately prior to any loading, unloading or transfer operation so as to minimise the emission of dust. AEC
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• Every belt-conveyor used for the transfer of dusty materials should be covered. Every transfer point between any two belt-conveyors should be totally enclosed.
• Any skip hoist for the transport of construction wastes should be properly enclosed.
• Vehicle washing facilities, including a high-pressure water jet, should be provided at the designated vehicle exit point. Every vehicle should be washed immediately before leaving the construction site to remove any dust materials from its wheels and body.
• The area where vehicle washing takes place and the section of the road between the washing facilities and the exit point, as well as the main haul road to the construction site should be paved with concrete, bituminous materials, hardcore or metal plates and kept clear of dusty materials.
• The main haul road to the site should be paved or sprayed with water frequently to keep the entire road surface wet and to minimise dust generation.
Through the implementation of the above control measure, dust levels will be reduced. The mitigated emission factors are given in Table 5.1. The maximum predicted mitigated suspended particulate concentrations at the representative ASRs are presented in Tables 5.2.
Table 5.1 Emission Factors for Various Construction Activities – With Mitigation Emission Factors Activities Remarks TSP RSP With 50% reduction of (1) Material unmitigated emission 2.17 x 10-3 g s-1 1.03 x 10-3 g s-1 Handling rate by frequent water suppression With 50% reduction of (2) Rock unmitigated emission 1.84 x 10-6 g s-1 9.59 x 10-7 g s-1 Breaking rate by frequent water suppression With 50% reduction of unmitigated emission (3) Excavation 5.78 x 10-3 g s-1 2.73 x 10-3 g s-1 rate by frequent water suppression With 85% reduction of (4) Vehicle unmitigated emission Movements on 1.73 x 10-1 g s-1 4.68 x 10-2 g s-1 rate by frequent water Unpaved Site suppression or using Roads paved road With 50% reduction of unmitigated emission (5) Wind Erosion 1.348 x 10-6 g s-1m-2 6.74 x 10-7 g s-1m-2 rate by frequent water suppression = (1)+(2)+(3)+(4) + (5) Total Emission 1.04 x 10-5 g s-1m-2 3.20 x 10-6 g s-1m-2 Total site area
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Table 5.2 Maximum Predicted TSP and RSP Concentrations – With Mitigation ASR 1- hour Averaged TSP 24-hour Averaged TSP 24-hour Averaged RSP ID Concentration, µg/m3 Concentration, µg/m3 Concentration, µg/m3 G/F 2/F G/F 2/F G/F 2/F A1 226.04 140.80 114.29 94.40 63.84 57.72 A2 179.25 146.62 102.59 93.91 60.24 57.57 A3 239.49 179.06 119.36 99.40 65.40 59.26 A4 183.61 132.64 111.36 98.93 62.94 59.12 A5 230.27 135.41 116.88 98.95 64.64 59.12 A6 194.39 142.10 110.64 98.86 62.72 59.10 A7 235.07 139.05 123.44 100.29 66.66 59.53 A8 473.43 159.68 209.30 104.94 93.08 60.98 A9 412.48 168.46 197.00 105.68 89.29 61.20 A10 254.74 153.92 135.86 98.25 70.48 58.91 Remarks: Results include annual TSP background level of 83.6µg/m3. TSP – recommended 1-hour TSP criterion (500µg/m3) and AQO for 24-hour TSP (260µg/m3) Results include annual RSP background level of 54.4µg/m3. RSP - AQO for 24-hour RSP (180µg/m3)
The assessment results indicated that the recommended hourly TSP criterion and the respective AQOs for TSP and RSP will not be exceeded at any of the representative ASRs with the implementation of the proposed dust control measures. Therefore, it is anticipated that with the adoption of appropriate mitigation measures, the construction of proposed drainage diversion works would not cause any adverse air quality impacts on nearby sensitive receivers. The isopleths of maximum hourly TSP and daily RSP at ground floor after mitigation are illustrated in Figure 4.3 and 4.4.
5.2 Noise
To minimise the construction noise impact on the NSRs, the following mitigation measures are recommended during the construction phase of the proposed drainage diversion works:
i) Use of quiet alternative plant and working methods:
The use of quiet plant as an at-source mitigation measures can result in a significant reduction of noise levels generated by the construction works. The degree of reduction achieved is dependent on actual construction method and work schedule. The Sound Power Levels of the recommended quiet plant for the drainage diversion works as adapted from the British Standard, BS 5228:Part 1:1997, are given in Table 5.3.
Table 5.3 Sound Power Levels of Quiet PME Reference number on Quiet Equipment Sound Power BS5228 Part 1: 1997 Level (dBA) C3-97 Excavator 105 C9-27 Lorry 105 C6-32 Poker 100 C7-118 Mobile Crane 99 C6-35 Concrete lorry mixer 100
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ii) Use of purpose-built noise barrier:
To ensure that the construction noise impacts on nearby NSRs are mitigated to acceptable levels, purpose-built noise barrier shall be installed along the portion of the site boundary between the works area and the adjacent Tai Po Tsai Village. Heights of the noise barriers shall range from around 4.4 to 5.6m. In addition, it is recommended that movable barrier set up around noise sources shall be used to provide screening effect wherever practicable. Appendix H shows the location of the proposed purpose-built noise barrier along portion of the site boundary.
In view of the fact that the plant inventory and construction sequence proposed by the Contractor may differ from the assumptions adopted in the assessment, detailed design of appropriate noise mitigation measures should be proposed by the Contractor prior to the commencement of work in order to ensure the potential construction noise impacts on nearby sensitive receivers are reduced to acceptable levels.
iii) Scheduling of work
Scheduling of work can reduce the noise impact on the NSRs. Good scheduling of works shall include minimising noisy operations; avoiding simultaneous operation of noisy equipment; making use of the existing physical barrier. Ensure works will only be carried out within non-restrictive hours.
iv) Sitting of facilities
PME should be sited as far as practicable from noise sensitive receivers. Consideration should also be given to using structures such as site offices and stores as noise barriers.
With the implementation of the above mitigation measures, the potential construction noise impacts on the NSRs will be significantly alleviated. Calculation of mitigated construction noise levels are detailed in Appendix G. The maximum predicted mitigated noise levels at the representative NSRs are summarised in Table 5.4.
Table 5.4 Maximum Predicted Mitigated Construction Noise Levels
Receiver ID Noise criteria Predicted Noise level, Leq (30min) , dB(A) Leq (30min), Stage 1 Stage 2 Stage 3 Stage 4 dB(A) N1 75 57 64 62 63 N2 75 60 67 65 66 N3 75 66 73 71 72 N4* 75 68 75 73 74 N5* 75 68 75 73 74 N6* 75 68 75 73 74 N7 70 58 65 63 64 N8 75 65 72 70 71 N9 75 64 71 69 70 N10 70 56 63 61 62 * The predicted noise levels after the use of purpose-built noise barrier
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The construction noise assessment results indicate that with the use of quiet plants and purpose-built noise barriers, the maximum predicted noise levels at all NSRs are in compliance with the daytime construction noise criteria. Therefore, it is anticipated that with the adoption of appropriate mitigation measures, the construction of proposed drainage diversion works would not cause any adverse noise impacts on nearby sensitive receivers.
5.3 Ecology
To minimise sedimentation and possible induced impacts on filling of stream meander, landform and filling engineering activities shall preferably be performed in dry seasons. It is recommended to build temporary sediment pool or install other appropriate sedimentation facility to treat water runoff from the construction site before discharge to down stream.
If land formation works could not be avoided in wet seasons, it is recommend to implement appropriate mitigation measures, such as installing silt traps, to reduce the potential impact due to sedimentation. Also, EPD’s guidelines to control construction site runoff shall be followed and potential soil erosion problem in the affected stream course shall be monitored during the construction works.
Loss of vegetation due to this proposed development will be compensated by the proposed landscaping scheme which would maximise plantation of trees and shrubs onsite. According to the proposed landscape master plan, all of the approximately 83 existing trees would be retained in-situ and approximately 1229 heavy standard trees would be planted on site and within 5m outside the eastern boundary of the site. Figure 1.2 shows the landscape master plan. Other practicable mitigation measures to minimise the potential impact on flora species include:
• To avoid removing existing native trees in the riparian habitat habitats; • Protection of trees identified for preservation through the use of protective fencing around the Condon Area (area designed to protect the tree root zone, trunk and crown from damage during the construction phase) and measures to prevent runoff from the construction site entering the preserved root zone; and • The health and condition of retained trees, and the condition of the tree protection measures to be regularly monitored throughout the construction phase.
The proposed tree planting would include native species as part of the project’s landscape proposals. A list of recommended species is provided in the table below. It is suggested that about 10 species of trees to be selected from the list according to availability of the nursery source. The recommended plant species would have certain ecological value in terms of plant ecology and the associated wildlife including birds. Detailed selection of the plant species shall be subject to agreement with relevant government departments.
Table 5.5 Recommended Plant Species To Be Planted For Landscaping Purpose Tree species Common Name Latin Name Camphor tree Cinnamomum camphora Chestnut oak Castanopsis fissa AEC
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Chinese alangium Alanglum chinense Chinese aralia Aralia chinensis Chinese banyan Ficus microcarpa Chinese hackberry Celtis sinensis Evodia Evodia lepta Ivy tree Schefflera octophylla Microcos Microcos paniculata Pond spice Litsea glutinosa Prickly ash zanthoxylum avicennae Rough-leaved stem fig Ficus hispida Red machilus Machilus thunbergil Superb fig Ficus superba Scarlet sterculia Sterculla lanceolata Tallow tree Sapium sebiferum Turn-in-the-wind Mallotus paniculatus
To adopt a more sustainable approach to development, the design of the landscaped areas adjacent to the proposed residential blocks will incorporate ecologically beneficial features wherever possible. This approach is adopted in the design of the proposed water pond on the eastern periphery of the site. This constructed and managed water pond would be inhabited by some stream fauna found in the area including species such as dragonflies, fishes and maybe amphibians. To improve habitat quality of the constructed pond habitat, some aquatic plants including submerged, floating, emergent and marginal plants, will be planted (refer to Landscape Plan for detailed species selection). Conceptual design of the water pond is given in Appendix I.
By creating pond habitat and introducing more native plants to the site, some wildlife such as birds, bats, and insects would be attracted to feed on, and the ecological value of the site would be enhanced.
To enhance the faunal diversity and ecological stability of the environment, it has been proposed in the Freshwater Fish Investigation Survey Report to restore the underground channel with irregular shaped substrata such as coarse sand and rocks along the bottom as an alternative to standard drainage design. Since the channel will eventually be handover to Drainage Services Department (DSD) for maintenance in the operational phase, the channel design shall be subject to DSD’s acceptance.
5.4 Waste
Good waste management practices will be implemented on site, including proper waste handling within the site, removal of waste material generated from the construction works, and implementation of any mitigation measures to avoid or minimize potential adverse impacts associated with waste arising from the construction of the drainage diversion works. In addition, waste minimisation and recycling practices will be employed wherever practicable on site to reduce generation of construction wastes. Disposal of waste shall be on a regular basis to avoid accumulation on site. Location of waste storage points shall be away from the existing dwellings and other municipal facilities where possible.
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The various waste management options can be categorized in terms of preference from an environmental viewpoint. The options considered to be more preferable have the least impacts and are more sustainable in the long term. Hence, the hierarchy is as follows:
• avoidance and minimization, i.e. not generating waste through changing or improving practices and design; • reuse of materials, thus avoiding disposal (generally with only limited reprocessing); • recovery and recycling, thus avoiding disposal (although reprocessing may be required); • treatment and disposal, according to relevant laws, guidelines and good practice; and • disposal, the release of wastes to air, water, or land in properly controlled or safe ways or so as to render them harmless.
5.4.1 Construction and Demolition (C&D) Material
The Contractor shall recycle C&D material on-site wherever practical. Proper segregation of wastes on site will increase the feasibility for recycling certain components of the waste stream by the recycling contractors.
The use of wooden hoardings shall not be allowed except where noise barriers are needed, and then these shall be of 20mm thick wood/ply. For elsewhere, alternative materials which can be reused or recycled, such as metal (aluminium, alloy, etc) hoarding, shall be used.
Different areas of the worksite shall be designated for such waste segregation and storage wherever site conditions permit.
Trip-ticket system should be established to monitor the disposal of C&D material and solid wastes at public filling facilities and landfills, in order to control fly-tipping.
5.4.2 Chemical Waste
For chemical waste produced from a process, as defined by Schedule 1 of the Waste Disposal (Chemical Waste) (General) Regulation, a ‘Chemical Waste Producer’ register should be made with EPD.
Chemical waste will be handled in accordance with the Code of Practice on the Packaging, Handling and Storage of Chemical Waste. Some requirements of the Code of Practice are outlined as follows.
Containers used for the storage of chemical waste will: (i) be suitable for the substance they are holding, resistant to corrosion, maintained in good condition, and securely closed; (ii) have a capacity of less than 450 litres unless the specification have been approved by the EPD; and (iii) display a label in English and Chinese in accordance with instruction prescribed in Schedule 2 of the Regulations.
The storage area for chemical wastes will: (i) be clearly labeled and used solely for the storage of chemical waste; (ii) be enclosed on at least three sides; (iii) have an impermeable floor and bunding, 110% capacity of the largest container or 20% of the storage capacity, whichever is the greatest;
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(iv) have adequate ventilation; (v) be covered to prevent rainfall entering (water collected within the bund must be tested and disposed as chemical waste if necessary); and (vi) be arranged so that incompatible materials are adequately separated.
Chemical waste will be disposed: (i) via a licensed waste collector; and (ii) to a facility licensed to receive chemical waste, such as the Chemical Waste Treatment Facility; or (iii) to a reuser of the waste, under the approval from the EPD.
5.4.3 General refuse
General refuse including food wastes, such as lunch box, and domestic wastes generated on- site will be stored in enclosed bins or compaction units separate from construction and chemical wastes. A waste collector listed in the Environmental Protection Department’s waste collectors directory will be employed to remove general refuse from the site, separately from construction and chemical wastes, on a daily or every second day basis to minimize odour, pest and litter impacts. No burning of refuse on site will be permitted.
A co-ordinator for the implementation of above waste management practices should be identified in the Waste Management Plan prepared for the construction of the drainage diversion works.
5.5 Water
To reduce the generation of silt-laden discharge and prevent uncontrolled runoff from the construction site, the following recommended mitigation measures shall be implemented on site during the construction of the proposed drainage diversion works:
• U-channel should be installed along the low end of the boundary of the site as necessary to collect all surface runoff within the site and divert the run off to sump pits to be pumped to desilting tanks; • Wheels of all vehicles and plants will be washed before they leave the site to prevent deposition of mud, debris, etc. on roads by them. Water used for wheel washing shall be recycled. Thus, the wastewater can be reused. • If possible, excavation works shall be planned to avoid rainy season so as to minimise the runoff and reduce the amount of soil that could be carried off site. • The site shall be kept clean and tidy to avoid construction material and waste being washed off site. • The hoarding gaps shall be tightly sealed to avoid the seepage of wastewater to outside the site. • Perimeter channels shall be provided at site boundaries (where necessary) to intercept storm-water runoff from outside the site so that it does not wash across the site. • Silt trap design shall conform to the guidelines laid down in Appendix A1 of ProPECC PN 1/942.
2 Practice Note For Professional Persons: Construction Site Drainage, Professional Persons Consultative Committee, 1994. AEC
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• Temporarily exposed slope surfaces and construction material stockpiles shall be covered with tarpaulin or similar fabric to prevent erosion. • Wastewater likely to be contaminated with oil or grease shall be passed through an oil separator or grease trap before entering the site drainage system. • Wastewater from toilets, kitchen, etc., if any, shall be discharged into a foul sewer or a sewage treatment facility. Alternatively, chemical toilets may be used for reducing wastewater discharge. • Any special works areas which may be provided for material storage should be surrounded by bunds. • Reduce the amount of water used to dampen any surfaces or stockpiles.
During the operational phase, wastewater generated from the residential development will be collected by properly designed on-site drainage system and transferred to a package treatment plant prior to discharge. This would ensure that the wastewater shall not cause any adverse impact on the water quality of the stream as well as the Conservation Area and Coastal Protection Area, where it passes through and finally discharges to.
6. ENVIRONMENTAL MONITORING AND AUDIT
6.1 Air
Monitoring and audit of the Total Suspended Particulates (TSP) levels should be carried out by the Contractor during the construction of the proposed drainage diversion works to ensure that any deteriorating air quality is readily detected and timely action is taken to rectify the situation.
For regular impact monitoring, the sampling frequency of at least once in every six-days, shall be strictly observed at the monitoring station for 24-hr TSP monitoring. For 1-hr TSP monitoring, the sampling frequency of at least three times in every six-days should be undertaken when the highest dust impact occurs.
The 1-hour and 24-hour TSP levels should be measured by following the standard high volume sampling method as set out in the Title 40 of the Code of Federal Regulations, Chapter 1 (Part 50), Appendix B.
HOKLAS accredited analytical laboratory shall be engaged to carry out the analysis of the used filters generated through the 1-hour and 24-hour TSP monitoring.
The 24-hour AQO for TSP is 260µg/m3, which should not be exceeded more than once per year. The 1-hour TSP criteria for construction dust as specified in the Technical Memorandum on Environmental Impact Assessment Process (TMEIA) is 500µg/m3.
6.2 Noise
Construction noise levels should be monitored in terms of thirty minutes A-weighted equivalent continuous sound pressure level (Leq(30min)) during 0700-1900hrs on a weekly basis. The sound level meter should be mounted on a tripod at a height of 1.2m and the AEC
DRAINAGE DIVERSION WORKS FOR COMPREHENSIVE RESIDENTIAL DEVELOPMENT AT VARIOUS LOTS IN DD 227 & DD 229, TAI PO TSAI, SAI KUNG - PROJECT PROFILE 27
microphone should be positioned at 1m away from the building façade of the noise sensitive receiver facing the construction site.
An integrated sound level meter and calibrator will be used for noise monitoring which should comply with the International Electrotechnical Commission (IEC) Publication 804:1985 (Type 1). The sound level meter will be used with the manufacturer recommended wind shield.
The construction noise level at the noise sensitive receiver should not exceed the recommended noise criteria of 75 dB(A).
6.3 Ecology
Construction of the proposed drainage diversion works must be conducted in an appropriately ecologically sensitive manner, with particular attention given to avoidance or minimization of disturbance through appropriate works scheduling and responsible works area maintenance.
Mitigation measures should be undertaken to reduce potential impacts associated with the proposed works. Careful monitoring of the proposed mitigation measures by an Environmental Specialist who is preferably be a member of the Hong Kong Institute of Environmental Impact Assessment with a minimum of 5 years experience of work in Hong Kong and preferably has a suitable background in natural history and a professional qualification in terrestrial ecology, is required to assess the effectiveness of mitigation measures.
6.4 Waste
The Contractor is required to prepare a comprehensive Waste Management Plan and a Waste Disposal Plan detailing recycling, storage, transportation and disposal strategy for the proposed drainage diversion works. Waste shall be reused on site as far as practicable in order to minimize waste generation and the associated impacts of waste disposal. It is anticipated that the majority of excavated material shall be reused on site or stockpiled for use during the construction of the proposed drainage diversion or for backfilling of the existing stream during site formation at a later stage. Excavated material shall be sorted on site, soil shall be used for landscaping. Detailed records of waste produced shall be kept in order to monitor disposal, and these records shall be audited. Regular site inspections shall be carried out to ensure effective implementation of the waste management practices.
6.5 Water
Potential water quality impacts associated with sedimentation of untreated site runoff during the construction of the proposed drainage diversion are the main concern. Since substantial site runoff usually occurs during heavy rainfall events, it is recommended that the excavation works should, if possible, preferably take place during dry seasons. The contractor shall implement the mitigation measures as detailed in Section 5.5 in order to minimize any potential impacts on water quality as a result of the proposed drainage diversion works.
AEC
DRAINAGE DIVERSION WORKS FOR COMPREHENSIVE RESIDENTIAL DEVELOPMENT AT VARIOUS LOTS IN DD 227 & DD 229, TAI PO TSAI, SAI KUNG - PROJECT PROFILE 28
Environmental monitoring shall be carried out, including inspections of stream courses and drains, to ensure effective implementation of mitigation measures during construction.
7. USE OF PREVIOUS APPROVED EIA REPORTS
No previous EIA report has been approved or submitted for the subject development.
8. CONCLUSIONS
8.1 Air
Without mitigation measures, air quality impacts associated with the construction of the drainage diversion works are predicted to exceed the air quality criteria at some of the nearby air sensitive receivers under the worst-case scenario. With the implementation of appropriate mitigation measures such as frequent water suppression and the use of paved roads, the potential construction air quality impacts are reduced to acceptable levels within the air quality criteria. It is anticipated that the short term impacts associated with fugitive dusts during the construction phase will not pose any adverse air quality impact on nearby sensitive receivers with the application of proper mitigation measures.
No operational phase air quality impact as a result of the proposed drainage diversion is anticipated.
8.2 Noise
Without mitigation measures, noise impacts associated with the construction of the drainage diversion works are predicted to exceed the noise criteria at some of the nearby sensitive receivers under the worst-case scenario. With the implementation of appropriate mitigation measures, including the use of quiet construction plant and erection of purpose-built noise barrier, the potential construction noise impacts are reduced to acceptable levels within the noise criteria. It is anticipated that the short term impacts associated with the construction activities will not pose any adverse noise impact on nearby sensitive receivers with the application of proper mitigation measures.
No operational phase noise impact as a result of the proposed drainage diversion is anticipated.
8.3 Ecology
The water quality of the existing stream within the subject site is stressed through the effect of pollution from various human activities in the past such as farming and construction works. Existing water pollution sources that are affecting the stream generally relate to the domestic effluents generated in the surrounding area.
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DRAINAGE DIVERSION WORKS FOR COMPREHENSIVE RESIDENTIAL DEVELOPMENT AT VARIOUS LOTS IN DD 227 & DD 229, TAI PO TSAI, SAI KUNG - PROJECT PROFILE 29
Findings of preliminary ecological review and freshwater fish investigation survey indicate that the existing terrestrial and aquatic environment of the stream section within the subject site is of a low ecological value and do not support rare or protected species.
During the proposed drainage diversion works, water flow in the existing stream section within the site shall be maintained until the construction of the new drainage channel is completed and ready for diversion. Therefore, the proposed drainage diversion would not introduce significant changes in hydrological characteristic in upper and lower stream course during both construction and operational phases.
After implementing appropriate mitigation measures, including installation of appropriate sedimentation facility and silt traps during the construction phase, tree planting and creating pond habitat at the future development, there shall be no adverse ecological impact associated with the proposed drainage diversion works.
8.4 Waste
The wastes which are likely to be generated during the construction of the drainage diversion are mainly Construction and Demolition (C&D) wastes and excavated materials. Majority of the excavated material shall be reused onsite for the construction of the proposed drainage diversion or backfilling the existing stream during site formation at a later stage.
Good waste management practice will be implemented on the site, including waste control within the site, removal of waste material generated due to the construction works, and implementation of any mitigation measures to avoid or minimize potential adverse impacts associated with waste arising from the drainage diversion works. In addition, waste minimisation and recycling practices will be employed wherever applicable on the site to reduce waste generation. Disposal of waste shall be on a regular basis to avoid accumulation on site. Locate waste storage points shall be away from existing dwelling and facilities where possible.
No operational phase waste impact as a result of the proposed drainage diversion is anticipated.
8.5 Water
Water pollution sources affecting the existing stream section within the subject site are generally related to the domestic effluents generated by the village houses at Tai Po Tsai Tsuen and other development upstream.
After implementing mitigation such as the provision of toilets, installation of appropriate wastewater treatment facility and other pollution control measures suggested in the content, the proposed drainage diversion works shall not cause any adverse impact on the water quality of the stream as well as the Conservation Area and Coastal Protection Area, where it passes through and finally discharges to.
AEC
Appendix A Tentative Development Programme for the Proposed Residential Development at Tai Po Tsai, Sai Kung
Appendix B Works Area Plan & Proposed Sequence of Drainage Diversion Works
Appendix C Preliminary Ecological Review Report
Drainage Diversion Works for Comprehensive Residential Development at Various Lots in DD 227 & DD 229, Tai Po Tsai, Sai Kung Ecological Review ------
Photo 1. Car park Photo 2. Leisure ground
Photo 4. Stream
Photo 3. Stream
Photo 5. Pavetta hongkongensis Photo 6. Pavetta hongkongensis
File:Photo 16 16/12/2003 14 Drainage Diversion Works for Comprehensive Residential Development at Various Lots in DD 227 & DD 229, Tai Po Tsai, Sai Kung Ecological Review ------
Photo 7. Waterfall Photo 8. Stream moth or estuarine
Photo 9. Rufous-backed Shrike Photo 10. Crested Myna
Photo 11. Black-necked Starling Photo 12. Spotted Dove
File:Photo 16 16/12/2003 15 Drainage Diversion Works for Comprehensive Residential Development at Various Lots in DD 227 & DD 229, Tai Po Tsai, Sai Kung Ecological Review ------
Photo 13. Performing night survey Photo 14. Common toad
Photo 15. Gunther’s frog Photo 16. Gunther’s frog
Photo 17. Dragonfly Photo 18. Dragonfly Orthethrum chrysis Orthethrum glaucum
File:Photo 16 16/12/2003 16 Drainage Diversion Works for Comprehensive Residential Development at Various Lots in DD 227 & DD 229, Tai Po Tsai, Sai Kung Ecological Review ------
Photo 19. Dragonfly Photo 20. Damselfly Orthethrum sabina Sabina Agriocnemis femina oryzae
Photo 21. Butterfly Photo 22. Butterfly Common HedgeBlue (Acytolepis puspa) Common Mapwing (Cyrestis thyodamas)
File:Photo 16 16/12/2003 17
Appendix D Freshwater Fish Investigation Survey Report
Appendix E Calculation Sheet of Emission Factors for Construction Dust Emission
Appendix F Sample Output Files of ISCST3 Model for Construction Dust Emission
Appendix G Worksheet of Construction Noise Prediction
PART A - Unmitigated Construction Noise Level from the Use of Powered Mechanical Equipment for Construction Work other than Percussive Piling
Site Reference: 600
Site Reference: Proposed Residential Development at Lot No.898 in D.D. 227, Tai Po Tsai, Sai Kung
STEP UNITS
1 NSR NSR as marked on attached plan NSR type Domestic Premises University Staff University Staff NSR location / address Quarter Residence Tai Po Tsai village Indicate by ticking the critical A1 A2 A3 NSRs to be assessed in details
2 Distance Slant distance between A1 A2 A3 source and receiver for 222 162 75 m single notional source position
3 CNP PME Item Activity Code Description No. of items dB(A) per item Log sum 1 Mobilization and sheet 102 Generator, slienced 2 100 115 piling installation# 081 Excavator 2 112 2 Excavation & 001 Air compressor 1 100 123 Construction of box 102 Generator, slienced 2 100 culvert 081 Excavator 3 112 141 Lorry 3 112 170 Poker, vibratory, hand-held 2 113 186 Roller, vibratory 2 108 048 Mobile crane (diesel) 2 112 3 Connection works and 001 Air compressor 1 100 119 diversion 102 Generator, slienced 1 100 048 Mobile crane (diesel) 1 112 081 Excavator 1 112 141 Lorry 1 112 044 Concrete Lorry Mixer 1 109 047 Concrete pump 1 109 050 Concrete vibrator 2 105 4Backfilling & 001 Air compressor 1 100 120 compaction 102 Generator, slienced 1 100 081 Excavator 3 112 141 Lorry 3 112 186 Roller, vibratory 2 108 dB(A)
4 PNL (a) Distance attenuation correction A1 A2 A3 dB(A) factor from Step 2 & Table 5 of TM 55 52 46
(b) PNL from Step 3 & the above 1 60 63 69 dB(A) distance correction 2 68 71 77 3 646773 4 656874
5 Acoustic Details: facade effect 3 dB(A) reflection correction
6 CNL (4b) + (5) = 1 63 66 72 dB(A) 2717480 3677076 4687177 7 Criterion 75 75 75 dB(A) #Remark: Sheet piling installation shall be carried out by using hydraulic type percussive piling method. Since noise produced by percussive piling is controlled under the Noise Control Ordinance, construction noise permit shall be applied by the contractor before commencement of work. PART B - Unmitigated Construction Noise Level from the Use of Powered Mechanical Equipment for Construction Work other than Percussive Piling
Site Reference: 600
Site Reference: Proposed Residential Development at Lot No.898 in D.D. 227, Tai Po Tsai, Sai Kung
STEP UNITS
1 NSR NSR as marked on attached plan NSR type Domestic Premises Tai Po Tsai Tai Po Tsai Tai Po Tsai NSR location / address village village village HKUST Indicate by ticking the critical B4 B5 B6 B7 NSRs to be assessed in details
2 Distance Slant distance between B4 B5 B6 B7 source and receiver for 48 21 46 206 m single notional source position
3 CNP PME Item Activity Code Description No. of items dB(A) per item Log sum 1 Mobilization and sheet 102 Generator, slienced 2 100 115 piling installation# 081 Excavator 2 112 2 Excavation & 001 Air compressor 1 100 123 Construction of box 102 Generator, slienced 2 100 culvert 081 Excavator 3 112 141 Lorry 3 112 170 Poker, vibratory, hand-held 2 113 186 Roller, vibratory 2 108 048 Mobile crane (diesel) 2 112 3 Connection works and 001 Air compressor 1 100 119 diversion 102 Generator, slienced 1 100 048 Mobile crane (diesel) 1 112 081 Excavator 1 112 141 Lorry 1 112 044 Concrete Lorry Mixer 1 109 047 Concrete pump 1 109 050 Concrete vibrator 2 105 4Backfilling & 001 Air compressor 1 100 120 compaction 102 Generator, slienced 1 100 081 Excavator 3 112 141 Lorry 3 112 186 Roller, vibratory 2 108 dB(A)
4 PNL (a) Distance attenuation correction B4 B5 B6 B7 dB(A) factor from Step 2 & Table 5 of TM 42 34 41 54
(b) PNL from Step 3 & the above 1 73 81 74 61 dB(A) distance correction 2 81 89 82 69 3 77857865 4 78867966
5 Acoustic Details: facade effect 3 dB(A) reflection correction
6 CNL (4b) + (5) = 1 76 84 77 64 dB(A) 2 84 92 85 72 3 80 88 81 68 4 81 89 82 69 7 Criterion 75 75 75 70 dB(A) #Remark: Sheet piling installation shall be carried out by using hydraulic type percussive piling method. Since noise produced by percussive piling is controlled under the Noise Control Ordinance, construction noise permit shall be applied by the contractor before commencement of work. PART C - Unmitigated Construction Noise Level from the Use of Powered Mechanical Equipment for Construction Work other than Percussive Piling
Site Reference: 600
Site Reference: Proposed Residential Development at Lot No.898 in D.D. 227, Tai Po Tsai, Sai Kung
STEP UNITS
1 NSR NSR as marked on attached plan NSR type Domestic Premises Clearwater Bay NSR location / address Tai Po Tsai village Tai Po Tsai village school Indicate by ticking the critical C8 C9 C10 NSRs to be assessed in details
2 Distance Slant distance between C8 C9 C10 source and receiver for 84 101 250 m single notional source position
3 CNP PME Item Activity Code Description No. of items dB(A) per item Log sum 1 Mobilization and sheet 102 Generator, slienced 2 100 115 piling installation# 081 Excavator 2 112 2 Excavation & 001 Air compressor 1 100 123 Construction of box 102 Generator, slienced 2 100 culvert 081 Excavator 3 112 141 Lorry 3 112 170 Poker, vibratory, hand-held 2 113 186 Roller, vibratory 2 108 048 Mobile crane (diesel) 2 112 3 Connection works and 001 Air compressor 1 100 119 diversion 102 Generator, slienced 1 100 048 Mobile crane (diesel) 1 112 081 Excavator 1 112 141 Lorry 1 112 044 Concrete Lorry Mixer 1 109 047 Concrete pump 1 109 050 Concrete vibrator 2 105 4Backfilling & 001 Air compressor 1 100 120 compaction 102 Generator, slienced 1 100 081 Excavator 3 112 141 Lorry 3 112 186 Roller, vibratory 2 108 dB(A)
4 PNL (a) Distance attenuation correction C8 C9 C10 dB(A) factor from Step 2 & Table 5 of TM 47 48 56
(b) PNL from Step 3 & the above 1 68 67 59 dB(A) distance correction 2 76 75 67 3 727163 4 737264
5 Acoustic Details: facade effect 3 dB(A) reflection correction
6 CNL (4b) + (5) = 1 71 70 62 dB(A) 2 79 78 70 3 757466 4 76 75 67 7 Criterion 75 75 70 dB(A) #Remark: Sheet piling installation shall be carried out by using hydraulic type percussive piling method. Since noise produced by percussive piling is controlled under the Noise Control Ordinance, construction noise permit shall be applied by the contractor before commencement of work. PART A - Mitigated Construction Noise Level from the Use of Quiet Powered Mechanical Equipment for Construction Work other than Percussive Piling
Site Reference: 600
Site Reference: Proposed Residential Development at Lot No.898 in D.D. 227, Tai Po Tsai, Sai Kung
STEP UNITS
1 NSR NSR as marked on attached plan NSR type Domestic Premises University Staff University Staff NSR location / address Quarter Residence Tai Po Tsai village Indicate by ticking the critical A1 A2 A3 NSRs to be assessed in details
2 Distance Slant distance between A1 A2 A3 source and receiver for 222 162 75 m single notional source position
3 CNP PME Item Activity Code Description No. of items dB(A) per item Log sum 1 Mobilization and sheet 102 Generator, silenced 2 100 109 piling installation# C3-97 Excavator * 2 105 2 Excavation & 001 Air compressor 1 100 116 Construction of box 102 Generator, silenced 2 100 culvert C3-97 Excavator * 3 105 C9-27 Lorry * 3 105 C6-32 Poker * 2 100 186 Roller, vibratory 2 108 C7-118 Mobile crane * 2 99 3 Connection works and 001 Air compressor 1 100 114 diversion 102 Generator, silenced 1 100 C7-118 Mobile crane * 1 99 C3-97 Excavator * 1 105 C9-27 Lorry * 1 105 C6-35 Concrete Lorry Mixer * 1 100 047 Concrete pump 1 109 050 Concrete vibrator 2 105 4Backfilling & 001 Air compressor 1 100 115 compaction 102 Generator, silenced 1 100 C3-97 Excavator * 3 105 C9-27 Lorry * 3 105 186 Roller, vibratory 2 108 * Sound Power Levels of quiet PME based on the BS 5228 : Part 1 : 1997. dB(A)
4 PNL (a) Distance attenuation correction A1 A2 A3 dB(A) factor from Step 2 & Table 5 of TM 55 52 46
(b) PNL from Step 3 & the above 1 54 57 63 dB(A) distance correction 2 61 64 70 3 596268 4 606369
5 Acoustic Details: facade effect 3 dB(A) reflection correction
6 CNL (4b) + (5) = 1 57 60 66 dB(A) 2 646773 3 626571 4 636672 7 Criterion 75 75 75 dB(A) #Remark: Sheet piling installation shall be carried out by using hydraulic type percussive piling method. Since noise produced by percussive piling is controlled under the Noise Control Ordinance, construction noise permit shall be applied by the contractor before commencement of work. PART B - Mitigated Construction Noise Level from the Use of Quiet Powered Mechanical Equipment and noise barrier for Construction Work other than Percussive Piling
Site Reference: 600
Site Reference: Proposed Residential Development at Lot No.898 in D.D. 227, Tai Po Tsai, Sai Kung
STEP UNITS
1 NSR NSR as marked on attached plan NSR type Domestic Premises Tai Po Tsai Tai Po Tsai Tai Po Tsai NSR location / address village village village HKUST Indicate by ticking the critical B4 B5 B6 B7 NSRs to be assessed in details
2 Distance Slant distance between B4 B5 B6 B7 source and receiver for 48 21 46 206 m single notional source position
3 CNP PME Item Activity Code Description No. of items dB(A) per item Log sum 1 Mobilization and sheet 102 Generator, silenced 2 100 109 piling installation# C3-97 Excavator * 2 105 2 Excavation & 001 Air compressor 1 100 116 Construction of box 102 Generator, silenced 2 100 culvert C3-97 Excavator * 3 105 C9-27 Lorry * 3 105 C6-32 Poker * 2 100 186 Roller, vibratory 2 108 C7-118 Mobile crane * 2 99 3 Connection works and 001 Air compressor 1 100 114 diversion 102 Generator, silenced 1 100 C7-118 Mobile crane * 1 99 C3-97 Excavator * 1 105 C9-27 Lorry * 1 105 C6-35 Concrete Lorry Mixer * 1 100 047 Concrete pump 1 109 050 Concrete vibrator 2 105 4Backfilling & 001 Air compressor 1 100 115 compaction 102 Generator, silenced 1 100 C3-97 Excavator * 3 105 C9-27 Lorry * 3 105 186 Roller, vibratory 2 108 * Sound Power Levels of quiet PME based on the BS 5228 : Part 1 : 1997. dB(A)
4 PNL (a) Distance attenuation correction B4 B5 B6 B7 dB(A) factor from Step 2 & Table 5 of TM 42 34 41 54
(b) PNL from Step 3 & the above 1 67 75 68 55 dB(A) distance correction 2 74 82 75 62 3 72807360 4 73817461
5 Temporary Height of Effective Noise Barrier 4.4 5.6 5 0 m Noise Noise Barrier Effect 2 10 3.3 0 dB(A) Barrier
6 Acoustic Details: facade effect 3 dB(A) reflection correction
7 CNL (4b) - (5) + (6) = 1 68 68 68 58 dB(A) 2 75757565 3 73737363 4 74747464 8 Criterion 75 75 75 70 dB(A) #Remark: Sheet piling installation shall be carried out by using hydraulic type percussive piling method. Since noise produced by percussive piling is controlled under the Noise Control Ordinance, construction noise permit shall be applied by the contractor before commencement of work. PART C - Mitigated Construction Noise Level from the Use of Quiet Powered Mechanical Equipment for Construction Work other than Percussive Piling
Site Reference: 600
Site Reference: Proposed Residential Development at Lot No.898 in D.D. 227, Tai Po Tsai, Sai Kung
STEP UNITS
1 NSR NSR as marked on attached plan NSR type Domestic Premises Tai Po Tsai Clearwater Bay NSR location / address village Tai Po Tsai village school Indicate by ticking the critical C8 C9 C10 NSRs to be assessed in details
2 Distance Slant distance between C8 C9 C10 source and receiver for 84 101 250 m single notional source position
3 CNP PME Item Activity Code Description No. of items dB(A) per item Log sum 1 Mobilization and sheet 102 Generator, silenced 2 100 109 piling installation# C3-97 Excavator * 2 105 2 Excavation & 001 Air compressor 1 100 116 Construction of box 102 Generator, silenced 2 100 culvert C3-97 Excavator * 3 105 C9-27 Lorry * 3 105 C6-32 Poker * 2 100 186 Roller, vibratory 2 108 C7-118 Mobile crane * 2 99 3 Connection works and 001 Air compressor 1 100 114 diversion 102 Generator, silenced 1 100 C7-118 Mobile crane * 1 99 C3-97 Excavator * 1 105 C9-27 Lorry * 1 105 C6-35 Concrete Lorry Mixer * 1 100 047 Concrete pump 1 109 050 Concrete vibrator 2 105 4 Backfilling & 001 Air compressor 1 100 115 compaction 102 Generator, silenced 1 100 C3-97 Excavator * 3 105 C9-27 Lorry * 3 105 186 Roller, vibratory 2 108 * Sound Power Levels of quiet PME based on the BS 5228 : Part 1 : 1997. dB(A)
4 PNL (a) Distance attenuation correction C8 C9 C10 dB(A) factor from Step 2 & Table 5 of TM 47 48 56
(b) PNL from Step 3 & the above 1 62 61 53 dB(A) distance correction 2 69 68 60 3676658 4686759
5 Acoustic Details: facade effect 3 dB(A) reflection correction
6 CNL (4b) + (5) = 1 65 64 56 dB(A) 2727163 3706961 4717062 7 Criterion 75 75 70 dB(A)
Appendix H Proposed Purpose-built Noise Barrier with the Application of Quiet PME
Appendix I Landscape Master Plan and Conceptual Design of Dragonfly Pond